JPH0971685A - Light-diffusing plastic additive and light-diffusing plastic composition - Google Patents

Abstract

(57) [Abstract] [Problem] It is added to plastics and has excellent light diffusion.
Further, the present invention provides an additive and a plastic composition which give a soft, warm and yellow-colored plastic plate. SOLUTION: The weight loss rate at 500 ° C is 0.3 to 10
A plastic additive for light diffusion comprising synthetic calcium carbonate having a weight percentage of 0.5 to 20 μm and an average particle diameter of 0.5 to 20 μm, and a plastic composition containing the additive.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light-diffusing plastic additive and a light-diffusing plastic composition containing the additive, and more specifically, for the purpose of light-diffusing a lighting cover, a lighting signboard, and various displays. A light-diffusing plastic additive consisting of special calcium carbonate added to the plastic, and a light yellowish color with excellent light-diffusing property that is evenly dispersed and has excellent light-diffusing property. The present invention relates to a light-diffusing plastic composition that can provide a plastic plate-like material that develops color.

[0002]

2. Description of the Related Art Generally, a transparent plastic for light diffusion represented by a (meth) acrylic resin, a styrene resin, a polycarbonate resin or a polyester resin is widely used as a cover for lighting equipment, various displays and the like. Among them, as the lighting cover, the use of a milky color semi-transparent plate is widely used both for indoor and outdoor purposes because of improved lighting efficiency and antiglare effect.
Further, in accordance with the PL law enforced from July 1995, the number of cases in which a glass that is dangerous when it breaks changes to a plastic that is safe even if it breaks, and there is a need for a light-diffusing plastic that has a higher directivity. . In addition, in order to obtain the effect of diffusing light in the direction necessary for the purpose of the light-diffusing plastic, a method of blending the above-mentioned resin with inert inorganic particles having a desired shape as a light-diffusing material is disclosed in Japanese Patent Publication No.
-2188, Japanese Patent Publication No. 1-22861, etc., and is generally used.

The physical properties necessary for using a light diffusing agent in order to obtain the effect of diffusing light are as follows:
It is necessary that the light source cannot be seen through and the light transmittance and the diffusivity are simultaneously satisfied. Therefore, the particles to be blended with the resin, if too small, the transmittance for giving sufficient light diffusivity decreases,
On the other hand, if it is too large, the transmittance is improved, but the light diffusivity is impaired, and not only the defect that the light source is transparent and easy to see appears, but also the contained coarse particles damage the resin or form spots when molding. In order to reduce the light diffusibility, particles having a particle size on the order of μm, good dispersibility, and controllable in particle size are required.

By the way, in general, light-diffusing plastics are used as a light-diffusing material, although inorganic particles exhibiting a white color (reflected light) on the plate and a white light color (transmitted light) on the plate are also used.
When mixed with resin from the viewpoint of directivity, the reflected light of the plate, that is, the color of the plate itself (reflected light) is highly white without yellowing as much as possible, and the light color of the plate (transmitted light) is yellowish. The light-diffusing material is eager for soft and warm colors.

However, in the conventional method, in order to make the light ray color of the plate yellow, a coloring dye of yellow is added to the plate, so that the color (reflected light) of the plate itself also turns yellow. It was not possible to obtain a light diffusing plate that gave a deteriorated impression and had high directivity.

[0006]

DISCLOSURE OF THE INVENTION In the method of incorporating inorganic particles such as calcium carbonate, barium sulfate, and talc, which are currently used in light-diffusing plastics, dispersibility,
Due to insufficient uniformity of the particles, not only a satisfactory balance of light transmittance and light diffusivity cannot be obtained, but also a highly directional light color can be produced. I could not do it. Therefore, the present invention has an extremely high light transmittance, a high light diffusivity, and maintains the color of the plate itself (reflected light) which is impossible with the prior art while maintaining a high white color. It is an object of the present invention to provide a light-diffusing plastic additive that produces a soft color or a warm color that emits light) to yellow, and a light-diffusing plastic composition containing the same.

[0007]

Means for Solving the Problems As a result of intensive studies aimed at achieving the above object, the present inventors have found that a synthetic carbonic acid having a weight loss rate at 500 ° C. within a specific range and an average particle diameter within a specific range. By using calcium, the plate has a very high light transmittance and a high light diffusivity, and the light color of the plate (transmitted light) is colored yellow while maintaining the color of the plate itself (reflected light) high white. The inventors have found that a light-diffusing plastic that produces a soft color or a warm color is provided, and completed the present invention.

That is, the first aspect of the present invention is a plastic additive for light diffusion comprising synthetic calcium carbonate having a weight loss rate at 500 ° C. of 0.3 to 10% by weight and an average particle size of 0.5 to 20 μm. To

The second aspect of the present invention is that the weight loss rate at 500 ° C. is 0.3 to 10% by weight and the average particle size is 0.5 to.
Each of the contents is a light-diffusing plastic composition obtained by blending a transparent plastic with a light-diffusing plastic additive made of synthetic calcium carbonate having a thickness of 20 μm.

Hereinafter, the present invention will be described in more detail. The transparent plastic for light diffusion of the present invention is not particularly limited, and a known transparent plastic is used.
It is preferable to use one or two or more selected from the group consisting of acrylic resin, polystyrene resin, polycarbonate resin, and polyester resin.

In the present invention, the synthetic calcium carbonate dispersed and contained in the above-mentioned transparent plastic has a weight loss rate at 500 ° C. of 0.3 to 10% by weight, preferably 1 to 5%.
% By weight, particularly preferably 1.5 to 3% by weight, and the average particle size is 0.5 to 20 μm, preferably 0.7 to 1
It is 5 μm, particularly preferably 1 to 8 μm. Although the object of the present invention is sufficiently achieved by this, the weight loss rate at 150 ° C. is 0.
05 to 2% by weight, preferably 0.1 to 1% by weight, particularly preferably 0.2 to 0.7% by weight. Calcium carbonate, which has been added to light-diffusing plastics in the past, is high-purity calcium carbonate used for applications such as reagents, or ground calcium carbonate obtained by crushing natural products. The percentages were less than 0.3% by weight and 0.05% by weight, respectively. Thus, the synthetic calcium carbonate used in the present invention is
It is distinguished from the one used conventionally. There is no particular limitation on the crystal form of the synthetic calcium carbonate used in the present invention, and it is possible to use at least one of a hexagonal calcite type crystal, an orthorhombic aragonite crystal, and a pseudo hexagonal vaterite type crystal. However, cubic, spherical calcite-type or vaterite-type calcium carbonate is preferable from the viewpoints of particle shape uniformity, particle dispersibility, stability, etc. Most preferred are calcite type calcium carbonate in shape and sphere.

When the weight loss rate of the synthetic calcium carbonate at 500 ° C. is less than 0.3% by weight, both the color tone (reflected light) and the light ray color (transmitted light) of the added transparent plastic plate show white. The object of the invention cannot be achieved. On the other hand, if it exceeds 10% by weight, the shape of the synthetic calcium carbonate becomes unstable, causing aggregation and poor dispersion, and when molding with the resin, the resin is scratched or spots are formed and the light is concentrated on the spots. Satisfactory light diffusivity and transparency cannot be imparted. Therefore, if the transmitted light is white, the reflected light is white, and if the transmitted light is yellow, the reflected light is also yellow, which is different from the conventional product. In order to develop color on
It is essential to use synthetic calcium carbonate having a weight loss rate in a specific range. That is, the synthetic calcium carbonate having a weight loss rate controlled in the above-mentioned specific range is soft and gives a warm yellow color.

Further, also in the average particle diameter of the synthetic calcium carbonate, if the average particle diameter is less than 0.5 μm, the light transmittance for giving sufficient light diffusing property is lowered, and conversely, if it exceeds 20 μm, the transmittance is improved. However, the light diffusivity is impaired, and a defect that the light source can be easily seen through appears, and the contained coarse particles damage the resin during molding, impair the smoothness of the resin surface, and form spots. It is not preferable because it reduces the diffusivity.

The method for producing the synthetic calcium carbonate in the present invention is not particularly limited, but a so-called carbon dioxide gas compounding method obtained by conducting carbon dioxide gas in an aqueous suspension of calcium hydroxide (hereinafter referred to as lime milk). Or lime milk, sodium carbonate, calcium carbonate and the like, a solution combination method obtained by the reaction of carbonates such as ammonium carbonate and the like, and the like, and any of these methods, The reaction condition is that the weight loss rate of the obtained calcium carbonate at 500 ° C. is 0.3 to 1
It is selected so as to be 0% by weight and have an average particle diameter of 0.5 to 20 μm.

For example, as in Japanese Patent Laid-Open No. 2-184518,
Cubic calcium carbonate having a uniform particle size starting from basic plate-like calcium carbonate, as in JP-A-5-201724.
A method of controlling the carbonation rate with crystalline calcium carbonate or the like obtained by carrying out a carbonation reaction in a medium system containing 80% or more of ethylene glycol, or a carbonate ion solution in which a reaction buffer (for example, sodium hydroxide) is dissolved By stirring and mixing (for example sodium carbonate) and calcium solution (for example calcium chloride) at a specific concentration at a specific temperature, the particle size is adjusted to any particle size, it has excellent dispersibility, and the weight loss rate is specified. And a method for preparing calcite-type cubic synthetic calcium carbonate in the range of 1).

The synthetic calcium carbonate used in the present invention is
In order to stabilize the particle shape, sodium hexametaphosphate,
Inorganic phosphates such as sodium tripolyphosphate, phosphoric acid compounds such as phosphoric acid esters, alkali metal salts of polymers and copolymers having a carboxyl group, ammonium salts and their partially neutralized salts, polymers and copolymers containing sulfone groups It is used after being surface-treated according to a conventional method in an amount of 0.01 to 10% by weight with respect to calcium carbonate, using one or more of alkali metal salts, ammonium salts and partially neutralized salts thereof. Is preferred.

The synthetic calcium carbonate used in the present invention contains a fibrin compound or the like in order to further improve the dispersibility.
Organic acids such as fatty acids, resin acids, acrylic acid, oxalic acid and citric acid, inorganic acids such as tartaric acid, phosphoric acid, condensed phosphoric acid and hydrofluoric acid,
One or more of such polymers, their salts, or surface treatment agents such as their esters, dispersants such as surfactants, coupling agents such as titanate coupling agents, silane coupling agents, etc. It is preferably used after surface treatment according to a conventional method. Among these treatment agents for increasing dispersibility, fatty acids represented by stearic acid and fibrin compounds represented by hydroxyethyl cellulose and carboxymethyl cellulose are more preferable.

The weight loss rate of the plastic additive for light diffusion in the present invention refers to the weight loss rate of calcium carbonate alone which constitutes the plastic additive for light diffusion. In the case of the agent, the weight loss rate of each of the surface-treated treatment agents is measured, and the weight loss rate obtained by subtracting the weight loss rate of the surface treatment agent from the weight loss rate of the surface-treated calcium carbonate is the weight loss rate in the present invention. Become. For example, the weight loss rate measured alone is 1
1% by weight of treating agent 1 of 00% by weight and a similar weight loss rate of 5
In the surface-treated calcium carbonate treated with 0.4% by weight of 0% by weight of the treating agent 2, when the weight loss rate of the surface-treated calcium carbonate is 3.5% by weight, the weight loss rate of the light-diffusing plastic additive in the present invention is Is calculated as 2.3% by weight from the following calculation formula. 3.5− (100 × 0.01 + 50 × 0.004) =
3.5-1.2 = 2.3 (wt%)

The amount of synthetic calcium carbonate added to the light diffusing plastic is 0.5 to 10 parts by weight, preferably 1 to 5 parts by weight, and more preferably 1.5 to 3. 5 parts by weight. When the amount of synthetic calcium carbonate added is extremely small, the obtained light diffusion effect tends to be inadequate, and when it is extremely large, the hiding property tends to increase and the light transmittance tends to decrease.

For the purpose of further enhancing the effect of the present invention, it is preferable to combine the features of the following formulas (a) to (c) with respect to the particle size of synthetic calcium carbonate. (A) 1.0 ≦ DP2 / DP4 ≦ 2.0 (b) 1.0 ≦ DP1 / DP5 ≦ 2.5 (c) (DP2-DP4) /DP3≦0.5 DP1: Laser type particle size distribution measuring instrument (Nikkiso Microtrac FRA) Measured from the large particle side in the particle size distribution measured using a particle size distribution of 10% of the total particle size (μ
m) DP2: Particle diameter (μm) of 25% cumulative weight weight calculated from the large particle side in the particle size distribution measured using a laser particle size distribution measuring device (Microtrac FRA manufactured by Nikkiso Co., Ltd.) DP3: Laser type particle size distribution measuring device (Nikkiso Microtrac FRA) Particle size of 50% cumulative weight calculated from the large particle side in the particle size distribution measured using
m) DP4: Particle diameter (μ) of cumulative total of 75% calculated from the large particle side in the particle size distribution measured using a laser particle size distribution analyzer (Microtrac FRA manufactured by Nikkiso Co., Ltd.)
m) DP5: 90% by weight cumulative particle diameter calculated from the large particle side in the particle size distribution measured using a laser particle size distribution analyzer (Microtrac FRA manufactured by Nikkiso Co., Ltd.)
m)

The plastic additive for light diffusion of the present invention is
Used in combination with other additives used in light-diffusing plastics such as pigments, dyes (eg optical brighteners, bluing agents), various stabilizers, antioxidants, processing aids, antistatic agents, etc. As a matter of course, some other light diffusing agent may be used in combination with the light diffusing plastic additive of the present invention, if necessary.

The light-diffusing plastic composition of the present invention comprises
When a plastic containing the above-described synthetic calcium carbonate dispersed therein, for example, a methyl methacrylate resin composition is prepared, a methyl methacrylate resin containing a predetermined amount of synthetic calcium carbonate is used in a Henschel mixer at 60 to 10%.
Mixing and stirring for 0 seconds, melt-kneading with an extruder, extruding into a plate shape at a resin temperature of 230 to 260 ° C. and molding with a roll or the like, or forming pellets with an extruder, and using it with an injection molding machine The plate of the plastic composition for light diffusion of the present invention can be obtained by, for example, a method of molding at ˜260 ° C.

According to the present invention, the plastic additive for light diffusion does not agglomerate at the stage of molding the plastic, and it is substantially coarse and does not contain agglomerated particles, so that it has good surface smoothness. It is possible to obtain a plastic composition for light diffusion, and also to have a very high light transmittance and high light diffusivity, and to make the color of the plate itself (reflected light) high white, which was impossible with the prior art. It is possible to provide a light-diffusing plastic that produces a soft color or a warm color in which the light ray color (transmitted light) of the plate develops yellow while maintaining it.

[0024]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. In addition, the measurement of each characteristic value in the Example followed the following method.

Weight loss rate at 1.500 ° C. and 150 ° C. After drying the sample at 110 ° C. for 3 hours, a thermobalance device (manufactured by Rigaku:
TG 8110) and heated at 10 ° C./min to 150
The weight loss rate when the temperature reached 500 ° C or 500 ° C was measured.

2. Average particle size Calcium carbonate aqueous suspension was dispersed for 60 seconds using an ultrasonic disperser (Nippon Seiki Seisakusho: US-300T),
Prepare an aqueous dispersion. Using a laser particle size distribution analyzer (manufactured by Nikkiso Co., Ltd .: Microtrac FRA) for the aqueous dispersion, the particle size (μm) with a cumulative weight of 50% calculated from the large particle side in the particle size distribution measured was taken as the average particle size. .

3. Total light transmittance is ASTM D-1003
According to -61T, it measured with the integrating sphere type HTR meter.

4. The light diffusivity was obtained by dividing the average of the light intensity transmitted at angles of 20 ° and 70 ° measured by a goniometer (HR-100 type manufactured by Murakami Color Research Laboratory Co., Ltd.) by the light intensity transmitted at an angle of 5 °. The value obtained was calculated as a percentage.

5. The smoothness (concavo-convexity of the surface) was evaluated by visually observing the light-diffusing plastic, and a 5-point perfect rating was performed.
The criteria for scoring smoothness are as follows. 5 points: No surface irregularities are visible and the surface is smooth. 4 points: Almost no fine irregularities are seen on a part of the surface. 3 points: Small irregularities can be seen on the entire surface of the statement, but there is no problem in practical use. 2 points: Small irregularities are seen on the entire surface, and coarse irregularities are partially present, which is a problem in practical use. 1 point: Coarse irregularities are present on the entire surface.

6. Yellowness index (SM-2, manufactured by Suga Test Instruments Co., Ltd.) was used to determine the yellowness index of reflected light and transmitted light. The higher the number, the more yellow.

Examples 1 to 4 sodium carbonate solution (carbonate solution) with a concentration of x mol / liter, calcium chloride solution (calcium ion solution) with a concentration of y mol / liter, and sodium hydroxide solution with a concentration of z mol / liter. (Reaction buffer) was prepared at 100 liters each.

The sodium hydroxide solution and the sodium carbonate solution were mixed to prepare a mixed solution, and the liquid temperatures of the mixed solution and the calcium chloride solution were both adjusted to T ° C. Next, 100 liters of an aqueous solution of calcium chloride was added dropwise to 200 liters of a mixed solution of a sodium hydroxide solution and a sodium carbonate solution, a carbonation reaction was carried out under stirring conditions, and the dropping supply was terminated after 1 second from the start of addition. After the dropping time θ 2 seconds, sodium hexametaphosphate corresponding to M weight% of the theoretical amount of calcium carbonate existing in the reaction system was added, and the mixture was further stirred for 5 minutes.

The water suspension of calcium carbonate prepared as described above is concentrated using a centrifugal dehydrator, water is added to the concentrated solution to dilute and agitate, and then the diluted solution is concentrated again using the centrifugal dehydrator. Then, it was dried at 110 ° C. to obtain the plastic additive for light diffusion of the present invention. The average particle size of the obtained plastic additive for light diffusion is A μm, the weight loss rate at 150 ° C. is B% by weight,
The weight loss rate at 500 ° C. was C% by weight. Further, the obtained plastic additive for light diffusion was treated with N-% by weight of stearic acid. Moreover, as a result of observation by SEM photographs and X-ray diffraction, it was confirmed that the obtained plastic additive for light diffusion was a substantially cubic calcite-type calcium carbonate. Table 1 shows the special values of the average particle size and the weight loss rate of the plastic additive for light diffusion obtained in this example. Tables 2 and 3 show the production conditions and characteristics of the plastic additive for light diffusion.

Example 5 A plastic additive for light diffusion was prepared in the same manner as in Example 1 except that the stearic acid treatment was changed to a hydroxyethyl cellulose (HEC) treatment. Moreover, as a result of observation by SEM photographs and X-ray diffraction, it was confirmed that the obtained plastic additive for light diffusion was a substantially cubic calcite-type calcium carbonate. Table 1 shows the special values of the average particle size and the weight loss rate of the plastic additive for light diffusion obtained in this example. Tables 2 and 3 show the production conditions and characteristics of the plastic additive for light diffusion.

Example 6 100 g of industrial slaked lime was charged into a flask having a capacity of 3 liters containing 2 kg of ethylene glycol while stirring to prepare a raw material slurry. At this time, the temperature of the slurry is 30
° C. Purity 10 while stirring this raw material slurry
0% carbon dioxide was introduced at a rate of 1 liter / minute. 6
After 7 minutes, the pH became 7.4 and the slurry gelled. The temperature at that time was 40 ° C. When this gel was heated in a dryer maintained at 110 ° C., the gel disintegrated in 1 hour and turned into a slurry. The slurry is filtered to remove methanol.
And washed at 110 ° C. The average particle size of the obtained plastic additive for light diffusion was A μm, the weight loss rate at 150 ° C. was B weight%, and the weight loss rate at 500 ° C. was C weight%. Further, the obtained plastic additive for light diffusion was treated with 1.0% by weight of stearic acid.

As a result of observation by SEM photograph and X-ray diffraction, it was confirmed that the crystal form of the obtained plastic additive for light diffusion was substantially spherical calcite type calcium carbonate. Table 1 shows the special values of the average particle size and the weight loss rate of the plastic additive for light diffusion obtained in this example. Tables 2 and 3 show the production conditions and characteristics of the plastic additive for light diffusion.

[0037]

[Table 1] A: Average particle size (μm) B: Weight loss rate at 150 ° C (% by weight) C: Weight loss rate at 500 ° C (% by weight)

[0038]

[Table 2] x: Concentration of carbonate ion solution (mol / liter) y: Concentration of calcium ion solution (mol / liter) z: Concentration of reaction buffer solution (mol / liter) θ ₁ : Time until completion of dropping supply (second) θ ₂ : Time from the end of dropping supply to the start of sodium hexametaphosphate addition (seconds) M: Addition amount of sodium hexametaphosphate (wt%) T: Reaction start temperature (° C) N: Surface treatment amount (wt%)

[0039]

[Table 3]

Examples 7 to 12 A plastic composition was prepared by the following method using the plastic additive for light diffusion obtained in Examples 1 to 6 and processed into a plate, and the optical properties of the plastic composition were obtained. Table 4 shows the special values and comprehensive evaluation related to.

Method for producing plastic composition: 100 parts by weight of a partial copolymer of methyl methacrylate (polymerization rate: 18%) and 1.5 parts by weight of the plastic additive for light diffusion obtained in Examples 1 to 6 above. 2 parts by weight and 2.5 parts by weight were blended, and mixed and stirred at high speed for 60 seconds with a Henschel mixer to sufficiently disperse. Then, it was extruded into a sheet at a resin temperature of 250 ° C. using an extruder with a 65 mmφ vent and a coat hanger die having a die width of 600 mm, and processed into a plate having a thickness of 2 mm from a polishing triple roll.

Example 13 Polystyrene resin (manufactured by Dainippon Ink and Chemicals, Inc .: C
R3500) was mixed with 100 parts by weight of the plastic additive for light diffusion obtained in Example 1 at a ratio of 1.5 parts by weight, 2 parts by weight and 2.5 parts by weight and uniformly dispersed by a tumbler. This was subjected to an extruder in the same manner as in Example 7 to obtain a plate having a plate thickness of 2 mm. Table 4 shows the characteristic values and the comprehensive evaluation of the optical properties of the plastic composition.

Example 14 To 100 parts by weight of a polycarbonate resin (Novalex 7030 manufactured by Mitsubishi Chemical Co., Ltd.), 1.5 parts by weight, 2 parts by weight and 2 parts by weight of the plastic additive for light diffusion obtained in Example 1 were added. It was compounded in a ratio of 0.5 parts by weight and uniformly dispersed by a tumbler. This was subjected to an extruder in the same manner as in Example 7 except that the resin temperature was 290 ° C. to obtain a plate having a plate thickness of 2 mm. Table 4 shows the characteristic values and the comprehensive evaluation of the optical properties of the plastic composition.

[0044]

[Table 4]

Comparative Example 1 A sodium carbonate solution (carbonate ion solution) having a concentration of x mol / 1 liter, a calcium chloride solution (calcium ion solution) having a concentration of y mol / 1 liter, and a sodium hydroxide solution having a concentration of z mol / liter. (Reaction buffer) 10 each
0 liter was prepared. The sodium hydroxide solution and the sodium carbonate solution were mixed to prepare a mixed solution, and the liquid temperature of both the mixed solution and the calcium chloride solution was adjusted to T ° C.

Next, 100 liters of an aqueous solution of calcium chloride was added dropwise to 200 liters of a mixed solution of a sodium hydroxide solution and a sodium carbonate solution, a carbonation reaction was carried out under stirring conditions, and the dropping supply was finished 1 sec after the start of addition. After the dropping time θ 2 seconds, sodium hexametaphosphate corresponding to M weight% of the theoretical amount of calcium carbonate existing in the reaction system was added, and the mixture was further stirred for 5 minutes.

The aqueous suspension of calcium carbonate prepared as described above is concentrated using a centrifugal dehydrator, water is added to the concentrated liquid to dilute and agitate, and then the diluted liquid is concentrated again using the centrifugal dehydrator. Then, it was dried at 110 ° C. The average particle size of the obtained calcium carbonate is A μm, and the weight loss rate at 150 ° C. is B weight%, 5
The weight loss rate at 00 ° C. was C% by weight. Further, the obtained calcium carbonate was treated with stearic acid at D% by weight. As a result of observation by X-ray diffraction, it was confirmed that the crystal form of the obtained calcium carbonate was almost calcite. Table 5 shows the special values of the average particle size and the weight loss rate of calcium carbonate of this comparative example. Table 6 shows the conditions for producing calcium carbonate, and Table 7 shows the characteristics of the particle size of calcium carbonate.

Comparative Example 2 A plastic additive for light diffusion was prepared in the same manner as in Comparative Example 1 except that the sodium carbonate solution (carbonate ion solution) was changed to ammonium carbonate. In addition, as a result of observation by SEM photographs and X-ray diffraction, it was confirmed that the obtained plastic additive for light diffusion was substantially rhombohedral calcite-type calcium carbonate. Table 5 shows the special values of the average particle diameter and the weight loss rate of the plastic additive for light diffusion of this comparative example. Tables 6 and 7 show the manufacturing conditions and characteristics of the plastic additive for light diffusion.

Comparative Example 3 A special grade reagent calcium carbonate (manufactured by Wako Pure Chemical Industries, Ltd.) was used. The calcium carbonate of this comparative example was treated with stearic acid at N% by weight. In addition, as a result of observation by SEM photographs and X-ray diffraction, it was confirmed that the obtained plastic additive for light diffusion was substantially rhombohedral calcite-type calcium carbonate. Table 5 shows the special values of the average particle diameter and the weight loss rate of the plastic additive for light diffusion of this comparative example. Tables 6 and 7 show the manufacturing conditions and characteristics of the plastic additive for light diffusion.

Comparative Example 4 Heavy calcium carbonate (R heavy carbon: manufactured by Maruo Calcium Co., Ltd.) was used. The calcium carbonate of this comparative example was treated with stearic acid at N% by weight. Further, as a result of observation by SEM photographs and X-ray diffraction, it was confirmed that the obtained plastic additive for light diffusion was a calcite-type calcium carbonate having an indefinite shape. Table 5 shows the special values of the average particle diameter and the weight loss rate of the plastic additive for light diffusion of this comparative example.
Described in. Tables 6 and 7 show the manufacturing conditions and characteristics of the plastic additive for light diffusion.

Comparative Example 5 CO ₂ was added to 20 liters of lime milk having a liquid temperature of 30 ° C. and a specific gravity of 1.1.
Carbonization was carried out by passing a gas having a concentration of 25% at a flow rate of 1000 liters / hr at 85% of the theoretical carbonation rate to perform carbonation.
Of calcium carbonate was obtained. Further, the obtained calcium carbonate was treated with N% by weight of stearic acid. As a result of observation by SEM photographs and X-ray diffraction, the obtained plastic additive for light diffusion was found to be spindle-shaped calcite-type calcium carbonate containing about 10% slaked lime (Ca (OH) ₂ ). confirmed. Table 5 shows the special values of the average particle diameter and the weight loss rate of the plastic additive for light diffusion of this comparative example. Tables 6 and 7 show the manufacturing conditions and characteristics of the plastic additive for light diffusion.

[0052]

[Table 5]

[0053]

[Table 6] x, y, z, θ ₁ , θ ₂ , M, T and N are the same as in Table 2.

[0054]

[Table 7]

Comparative Examples 6 to 10 A light diffusing plastic composition was prepared in the same manner as in Examples 7 to 12 except that the light diffusing plastic additives of Comparative Examples 1 to 5 were used. Table 8 shows the characteristic values and evaluations relating to the optical properties of the processed plastic composition for light diffusion.

Comparative Example 11 A light-diffusing plastic was prepared in the same manner as in Comparative Example 8 except that 0.05 part of a yellow coloring dye (Dialene Di-Hello, manufactured by Mitsubishi Chemical Corporation) was mixed in the calcium carbonate of Comparative Example 3. The composition was prepared, processed into a plate, and the characteristic values and the comprehensive evaluation of the optical properties of the plastic composition for light diffusion are shown in Table 8. The optical characteristics of the light-diffusing plastic composition obtained in this comparative example are that reflected light and transmitted light are also yellow, the reflected light obtained in Examples 7 to 14 is highly white, and the transmitted light is colored yellow. It was different from the example.

[0057]

[Table 8]

[0058]

As described above, the plastic additive for light diffusion of the present invention does not agglomerate at the stage of molding a plastic, and is substantially coarse and does not contain agglomerated particles. It is possible to obtain a plastic composition for light diffusing having smoothness, and also has extremely excellent high light transmittance and high light diffusing property, and the color of the plate itself (reflected light), which has been impossible with the prior art. The present invention provides a light-diffusing plastic that maintains a high white color and produces a soft color or warm color in which the light ray color (transmitted light) of the plate develops yellow.

Claims (5)

[Claims] 1. The weight loss rate at 500 ° C. is 0.3 to 10.
A plastic additive for light diffusion, which is made of synthetic calcium carbonate having a weight% and an average particle diameter of 0.5 to 20 μm. 2. The weight loss rate at 150 ° C. is from 0.05 to
The plastic additive for light diffusion according to claim 1, which is 2.0% by weight. 3. A light-diffusing plastic composition obtained by adding the light-diffusing plastic additive comprising the synthetic calcium carbonate according to claim 1 to a transparent plastic. 4. The amount of the plastic additive for light diffusion added is 0.5 to 10 parts by weight with respect to 100 parts by weight of the transparent plastic.
The plastic composition for light diffusion according to claim 3, which is part by weight. 5. The light-diffusing plastic composition according to claim 3, wherein the light-diffusing plastic is at least one selected from the group consisting of (meth) acrylic resins, styrene resins, polycarbonate resins and polyester resins.